Method and device for reducing secondary brain injury

ABSTRACT

Disclosed is an apparatus and method for reducing secondary brain injury. The apparatus includes a brain-cooling probe and a control console. The brain-cooling probe cools the brain to prevent secondary injury by cooling the cerebrospinal fluid within one or more brain ventricles. The brain-cooling probe withdraws a small amount of cerebrospinal fluid from a ventricle into a cooling chamber located ex-vivo in close proximity to the head. After the cerebrospinal fluid is cooled it is then reintroduced back into the ventricle. This process is repeated in a cyclical or continuous manner in order to achieve and maintain a predetermined brain ventricle temperature lower than normal body temperature. The apparatus and method disclosed provides effective brain ventricle cooling without the need to introduce extra-corporeal fluids into the brain.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 10/243,583,filed Sep. 13, 2002, which claims the benefit of Provisional PatentApplication Ser. Nr.60/322,391 filed 2001 Sep. 14.

BACKGROUND

1. Field of Invention

This invention relates to a method and device for inducing globalcerebral hypothermia for the prevention of secondary brain injury fromstroke, trauma, or surgery.

2. Description of Prior Art

Patients suffering from stroke or head trauma, or have undergoneinvasive brain surgery are at risk from secondary brain injury.Secondary brain injury is a result of the innate healing response of thebrain to the original insult caused by several not completely understoodmechanisms. Regardless of the specific mechanisms involved, the endresult is swelling of the brain caused by edema, which can lead to acritical or terminal rise in intra-cranial pressure.

It has long been known that hypothermia is neuroprotective. Hypothermiahas a positive affect on all know mechanisms that lead to secondarybrain injury. Hypothermia is routinely used during brain and otherinvasive surgeries to protect the brain from surgical interruptions inblood flow. Hypothermia has also been shown to be effective incontrolling swelling of the brain in trauma and stroke patients.

The effectiveness of hypothermia is a function of depth and duration;the deeper the hypothermia, and/or the longer it is applied the moreneuroprotective it is. However, hypothermia has historically beenapplied systemically, and the depth and duration of hypothermia islimited by the patient's ability to tolerate the therapy.

Systemic hypothermia has historically been accomplished by immersion ofthe patient's body in a cool bath. Today there are several commercialsystemic hypothermia systems available. They consist of blankets or padswhere cooled water is circulated through channels in the walls of theblanket or pad, and the patient's body is maintained in intimatecontact. Medivan Corp. manufactures an example of a modern hypothermiasystem under the trade name Arctic Sun Cooling System.

Systemic hypothermia has been demonstrated to be effective in reducingsecondary injury from stroke, trauma, and surgery however, there areseveral drawbacks to this approach: 1) It takes several hours to lower apatient's body to therapeutic temperatures. This delay in achievingtherapeutic temperatures allows for the progression of irreversiblesecondary injury to the brain. 2) The practical therapeutic hypothermictemperature and duration is limited by the ability of the patient totolerate, or survive the therapy. 3) The side effects of systemichypothermia are frequent and can be life threatening, especially infrail patients. Side effects include shivering, cardiac arrhythmia andarrest, pneumonia, infections, and coagulation disorders. 4) The targetof hypothermia therapy is the brain; therefore inducing hypothermiasystemically places the patient at undue risk. 5) During the “criticalphase” (rewarming period) of hypothermia treatment, there is noeffective way to manage a sudden and critical increase in intra-cranialpressure, since re-cooling the body to reverse the increase inintra-cranial pressure takes several hours. 6) Systemic hypothermiaposes significant clinical and logistical patient management issues.

There are several examples in the art where catheters are constructedwith a cooling means, which is placed into the carotid artery to coolthe blood entering the head. This offers an advantage over systemichypothermia, since it provides a means to cool the head to lowertemperatures than the rest of the body, but it still results in systemichypothermia. Also, since the scientific evidence suggests thathypothermia must be maintained for extended periods of time, there is agreat risk that clots will form on the catheters and migrate into thebrain leading to episodes of stroke.

Nowhere in the art is it suggested that cooling the cerebrospinal fluidin a ventricle of the brain may induce global cerebral hypothermia andtherefore prevent secondary brain injury. Nowhere in the art is itsuggested that cerebral hypothermia can be accomplished by removing aportion of the cerebrospinal fluid from a brain ventricle, then coolingthe removed cerebrospinal fluid ex vivo, then reintroducing the cooledcerebrospinal fluid back into the brain ventricle in a continuous orcyclical manner.

SUMMARY

Therefore, it is an object of this invention to provide a method andapparatus for preventing secondary brain injury.

In accordance with one aspect of this invention, secondary brain injuryis prevented by placement of the distal end of a probe in to a ventricleof the brain and then, in a continuous or cyclical manner, using saidprobe to remove a portion of the cerebrospinal fluid contained in saidventricle into a cooling chamber located ex vivo at the proximal end ofsaid probe, then cooling said cerebrospinal fluid in the cooling chamberof said probe, then reintroducing said cooled cerebrospinal fluid backinto said ventricle, thereby cooling the brain while otherwisemaintaining normal temperature in the rest of the body. In accordancewith another aspect of this invention, secondary injury is prevented byplacement of the distal end of a probe into a ventricle of the brain,and then using said probe to cool the cerebrospinal fluid within saidventricle to a predetermined temperature for a predetermined time wheresaid probe functions in a continuous or cyclical manner to remove aportion of the cerebrospinal fluid contained in said ventricle into acooling chamber located ex vivo at the proximal end of said probe, thencooling said cerebrospinal fluid in the cooling chamber of said probe,then reintroducing said cooled cerebrospinal fluid back into saidventricle, thereby cooling the brain while otherwise maintaining normaltemperature in the rest of the body. In accordance with another aspectof this invention, secondary brain injury is prevented by placement ofthe distal end of a probe into a ventricle of the brain, and then usingsaid probe to cool the cerebrospinal fluid contained within saidventricle to a predetermined temperature, where then the temperature isincreased gradually over a period of time from the initial lowtemperature, to normal body temperature, with the period of time beinggreater than one hour and less than two months, where said probefunctions in a continuous or cyclical manner to remove a portion of saidcerebrospinal fluid contained in said ventricle into a cooling chamberlocated ex vivo at the proximal end of said probe, then cooling saidcerebrospinal fluid in said cooling chamber of said probe, thenreintroducing said cooled cerebrospinal fluid back into said ventricle,thereby cooling the brain while otherwise maintaining normal temperaturein the rest of the body. In accordance with another aspect of thisinvention, secondary brain injury is prevented by placement of thedistal end of a probe into a ventricle of the brain, and then using saidprobe to cool the cerebrospinal fluid within the ventricle to a degreebased on the physiological response to said cooling, where said probefunctions in a continuous or cyclical manner to remove a portion of thecerebrospinal fluid contained within said ventricle into a coolingchamber located ex vivo at the proximal end of said probe, then coolingsaid cerebrospinal fluid in said cooling chamber of the probe, thenreintroducing said cooled cerebrospinal fluid back into said ventricle,thereby cooling the brain while otherwise maintaining normal temperaturein the rest of the body. In accordance with another aspect of thisinvention, apparatus for preventing secondary brain injury includes aprobe, an introducer sheath, a stereotaxic ventricle access needle, anda control console where the introducer sheath and stereotaxic ventricleaccess needle are constructed to integrally provide access to aventricle of the brain by standard stereotaxic neurosurgical means, andwhere the distal end of said probe is placed into said ventricle throughsaid introducer sheath, and where said probe functions in a continuousor cyclical manner to remove a portion of the cerebrospinal fluidcontained within said ventricle into a cooling chamber located ex vivoat the proximal end of said probe, then cooling said cerebrospinal fluidin said cooling chamber of said probe, then reintroducing said cooledcerebrospinal fluid back into said ventricle, thereby cooling the brainwhile otherwise maintaining normal temperature in the rest of the body,and where the control console provides said probe with a means to removecerebrospinal fluid from a ventricle of the brain, a means to coolcerebrospinal fluid, a means to reintroduce cerebrospinal fluid backinto said ventricle, and a means to control said process of removing,cooling, and reintroducing cerebrospinal fluid. In accordance withanother aspect of this invention, apparatus for preventing secondarybrain injury includes a probe as described above where the distal end ofthe probe contains a mechanism near the distal tip of said probe tosense the temperature of cerebrospinal fluid contained in a ventricle ofthe brain. In accordance with another aspect of this invention,apparatus for preventing secondary brain injury includes a probe asdescribed above where the distal end of the probe contains a mechanismnear the distal tip of said probe to sense the pressure of cerebrospinalfluid contained in a ventricle of the brain. In accordance with anotheraspect of this invention, apparatus for preventing secondary braininjury includes a probe as described above where said probe provides fora means to drain excess cerebrospinal fluid from the ventricle of thebrain. In another aspect of this invention, apparatus for preventingsecondary brain injury includes a probe as described above, and anintroducer sheath as described above, where said probe and saidintroducer sheath are constructed to integrally provide for an extendedperiod of cooling and indwelling in a ventricle of the brain, with theperiod of cooling and indwelling being greater than one hour, and aslong as two months.

OBJECTS AND ADVANTAGES

Accordingly, besides the objects and advantages of the method andapparatus to prevent secondary brain injury described in my patentabove, several objects and advantages of the present invention are:

-   -   (a) to provide global cerebral hypothermia to a brain at risk of        secondary injury to the degree that offers maximum clinical        benefit without inducing hypothermia in the rest of the body;    -   (b) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the method for inducing hypothermia takes        advantage of the fact that the cerebrospinal fluid in a        ventricle of the brain can be cooled by a small caliber probe,        and brain tissue surrounding the ventricle may be cooled by heat        conduction into the ventricle to the extent that prevents        secondary injury.    -   (c) to provide global cerebral hypothermia to a brain at risk of        secondary injury within a minimal time after patient        presentation where therapeutic temperatures are achieved rapidly        due to the fact that only the brain is cooled;    -   (d) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the degree of hypothermia is adjusted        according to the physiological response to hypothermia, where        the physiological response to hypothermia is a change in        intra-cranial pressure;    -   (e) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the degree of hypothermia is adjusted        according to the physiological response to hypothermia, where        the physiological response to hypothermia is a change in patient        symptoms.    -   (f) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the degree of hypothermia is adjusted        according to the physiological response to hypothermia, where        the physiological response to hypothermia is a change in        localized blood perfusion;    -   (g) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the degree of hypothermia is adjusted        according to the physiological response to hypothermia, where        the physiological response to hypothermia is a change in the        size of the volume of infarcted tissue;    -   (h) to provide global cerebral hypothermia to a brain at risk of        secondary injury where the degree of hypothermia is adjusted        according to the physiological response to hypothermia, where        the physiological response to hypothermia is a change in blood        chemistry.    -   (i) to provide apparatus for inducing global cerebral        hypothermia to a brain tissue at risk of secondary injury        according to the objectives stated above;    -   (j) to provide a brain cooling probe system that consists of a        brain cooling probe, an introducer sheath, a stereotaxic        ventricle access needle, and a control console;    -   (k) to provide a brain cooling probe system that is constructed        to cool the cerebrospinal fluid contained within a ventricle of        the brain where said cooling means is ex vivo;    -   (l) to provide a brain cooling probe system that is constructed        to be placed into a ventricle of the brain by stereotaxic        radiological guidance using well known surgical methods;    -   (m) to provide a brain cooling probe system that is constructed        to provide for long term cooling and indwelling;    -   (n) to provide a brain cooling probe system that is constructed        to provide for fixation to the head of the patient;    -   (o) to provide a brain cooling probe system that is constructed        to provide for protection against infection;    -   (p) to provide a brain cooling probe system that is constructed        to provide for a means to sense a response to cooling;    -   (q) to provide a brain cooling probe system that is constructed        to provide for a means to control the degree of cooling applied        to the surrounding brain tissue.

DRAWING FIGURES

FIG. 1 shows a sagittal section of a human head with the brain probe,cooling assembly and introducer sheath fixated to the head with thedistal end of the probe and the introducer sheath placed into aventricle of the brain.

FIG. 2A. shows a side view of the brain probe and cooling assembly. FIG.2B shows an end view of the brain probe and cooling probe FIG. 3 showsthe introducer sheath.

FIG. 4 shows a sectional view of the introducer sheath placement into aventricle of the brain with the stereotaxic ventricle access needle.

FIG. 5 shows a sectional view of the introducer sheath in operationalposition after the stereotaxic access needle has been removed.

FIG. 6 shows in schematic form the preferred embodiment of the integraloperation of the brain probe, cooling assembly and the control console.

FIG. 7 shows a partial sectional view of the cooling assembly.

FIG. 8 shows a sectional view of the cooling coil prior to formation ofthe coil.

FIG. 9 shows the cooling coil after formation of the coil.

FIG. 10A shows a sectional view of the construction of the coolingassembly. FIG. 10B and end view of the cooling assembly.

FIG. 11A shows a sectional view of the umbilical attachment to thecooling assembly. FIG. 11B shows the console plug assembly of theumbilical assembly.

FIG. 11C-11F show a sectional views of the console plug assembly. FIG.11G shows the interaction between the console plug assembly, and theconsole receptacle.

FIG. 12A shows a sectional view of the brain probe. FIG. 12B shows asectional view of the brain probe shaft.

FIG. 13 shows a bottom view of the brain probe depicting the brainprobe/introducer sheath docking mechanism.

FIG. 14 shows a sectional view of the introducer sheath.

FIG. 15A shows a view of the construction of the docking ring assembly.FIG. 15B shows a sectional view of the docking ring assembly.

FIG. 16 shows a sectional view of the introducer sheath tube assembly.

FIG. 17A shows a front view of the control console. FIG. 17B shows aside view of the control console.

FIG. 18 shows a view of the cooling assembly mounting plate.

DESCRIPTION FIG. 1-6 Preferred Operational Embodiments

FIG. 1 depicts, in simplified form, a section of the head 20 with abrain probe 1 and introducer sheath 2 in operational position andcooling assembly 3 mounted on the head 20 with self-tapping bone screws17. The distal end 7 of probe 1, and the distal end of introducer sheath2 is located in a lateral ventricle of the brain 6. Probe tube 13connects probe 1 to cooling assembly 3 and provides fluid communicationfrom the probe 1 to cooling assembly 3. The distal end 7 of probe 1contains a thermocouple 18 (FIG. 2B), which measures the temperature ofthe cerebrospinal fluid 19 contained in ventricle 6. The shaft 21 ofprobe 1 passes through the introducer sheath 2 introducer sheath tube 8and connects the distal end 7 of probe 1 to the sheath docking collar 24of probe 1 (See FIG. 8). Probe shaft 21 provides fluid communicationfrom the ventricle 6 to probe tube 13 which therefore provides fluidcommunication from ventricle 6 to cooling assembly 3. The probe andintroducer sheath 1&2 is fixated to the head 20 by outward expansion ofthe fixation plug 22 of introducer sheath 2 against the surgicallycreated craniotomy hole 23 in the skull 10. The fixating plug as 22seals the craniotomy hole 23 and prevents infection, providing for longterm indwelling (greater than 1 hour and as long as two months) of theprobe and introducer sheath 1&2 in the brain 5. Antiseptic pad 145provides further protection against infection. Fluid tube 15, stop cock9, and luer fitting 25 provides fluid communication from the ventricle 6via probe shaft 21 of probe 1, and cooling assembly 3 and provides fordrainage of excess cerebrospinal fluid from the ventricle. Acommercially available physiological pressure sensor 4 may be mounted toluer fitting 25 to monitor cerebrospinal fluid pressure. Electricalcable 12 connects the pressure sensor 4 to the pressure meter (notshown). The cooling assembly 3 is connected to control console 76 byumbilical 14. During operation a portion of cerebrospinal fluid 19 (1 ccto 20 cc) is drawn from ventricle 6 into cooling assembly 3 throughprobe 1 and probe tube 13. The cerebrospinal fluid drawn into coolingassembly 3 is then cooled to between 0 Deg. C. and 25 Deg. C. The cooledcerebrospinal fluid 19 is then reintroduced into the ventricle 6 viaprobe tube 13 and probe 1. This cycle is repeated as necessary until thetemperature within the ventricle 6 is between 10 Deg. C. and 36 Deg. C.as measured by thermocouple 18.

FIG. 2A depicts a side view of brain probe 1 and cooling assembly 3.FIG. 2B depicts an end view of brain probe 1 and cooling assembly 3.Probe tube 13 connects probe 1 to cooling assembly 3 and provides fluidcommunication from distal tip 7 of probe 1 to cooling assembly 3. Fluidtube 13 also contains thermocouple wires that connect thermocouple 18mounted on distal tip 7 of probe 1 to control console 76 via umbilical14. Fluid tube 15, stop cock 9 and luer fitting 25 provides for drainageof excess cerebrospinal fluid 19. Probe 1 consists of probe shaft 21,sheath expansion plug 29, sheath docking collar 24, and thermocouple 18.Fluid port 26 at distal end 7 of probe shaft 21 provides fluidcommunication from ventricle 6 (FIG. 1) into shaft 21. Thermocouple 18at distal end 7 of probe shaft 21 senses temperature of cerebrospinalfluid 19 in ventricle 6 (FIG. 1). Signals from thermocouple 18 are sentto control console 76 and are used to control brain cooling. Probe shaft21 connects distal end 7 of probe 1 to proximal end 31 of probe 1 andprovides fluid communication from distal end 7 to proximal end 31. Probeshaft 21 contains a fluid communication lumen 32, and thermocouple leadlumen 33 (FIG. 12 A & B). Sheath expansion plug 29 and sheath dockingcollar 24 work integrally with introducer sheath 2 to fixate the probe 1and introducer sheath 2 to the head 20 and to seal the craniotomy hole23 to prevent infection. Cooling assembly 3 is mounted to head 20(FIG. 1) with (4) mounting tabs 27, and self-tapping screws 17 (FIG. 1).Rubber feet 28 provides for hermetic sealing of screw 17 to preventinfection. Umbilical 14 connects cooling assembly 3 to control console76 and contains gas lines 35 & 36 for cooling, pneumatic line 37 foractuating cerebrospinal fluid removal and replacement, and thermocoupleleads 34 & 77 (FIG. 6). Umbilical retaining flange 161 secures umbilical14 to cooling assembly 3.

FIG. 3 depicts the introducer sheath 2. The introducer sheath 2 isplaced into a ventricle of the brain 6 through craniotomy hole 23(FIG. 1) with stereotaxic access needle 39 (FIG. 4) and probe 1 is thenplaced into the ventricle of the brain 6 through the introducer sheath2. The introducer sheath 2 provides for access to a ventricle bystandard stereotaxic surgical methods, and allows for removal andreplacement of probe 1 during the course of the treatment. Introducersheath 2 consists of sheath tube 8, housing 40, antiseptic pad 145, andprobe docking pins 42. Fixation plug 22, and probe sealing boss 41 areformed integrally with the introducer housing 40. The fixation plug 22works integrally with probe 1 to fixate the assembly to the head, andseal the craniotomy hole 23. The probe sealing boss 41 mates with thebottom surface of docking collar 24 of probe 1 and seals the assembly toprevent contamination and infection.

FIG. 4 depicts introducer sheath 2 placement into ventricle 6 with thestereotaxic access needle 39. The diameter of the stereotaxic accessneedle 39 is tapered at the distal tip to the diameter of the probeshaft 21 as shown. Proximal to the taper, the diameter of thestereotaxic needle 39 is sized to slidably fit the inside diameter ofthe introducer tube 8. Needle stop 43 pushes the introducer sheath intoventricle 6 when the stereotaxic access needle 39 is advanced. Theproximal end 44 of the stereotaxic access needle 39 is configured tofunction with various commercial stereotaxic needle guidance systems(not shown). FIG. 5 depicts the introducer sheath 2 in ventricle 6 afterthe stereotaxic access needle 39 (FIG. 5) is removed.

FIG. 6 depicts in schematic form the integral operation of probe 1,cooling assembly 3 and control consol 76. The functional components ofprobe 1 are probe shaft 21, fluid port 26, and thermocouple 18. Thefunctional components of the cooling assembly are cooling cylinder 72,piston 48, cooling coil assembly 47, and thermocouple 45. The controlconsole 76 contains control circuitry 53, motor shaft positiontransducer 54, motor 55, crank 56, connecting rod 57, pneumatic cylinder58, piston 59, AC power source 60, Transformer 61, low-pressure solenoidvalve 63, high-pressure solenoid valve 64, low-pressure line 65,low-pressure pneumatic line 68, umbilical connector 69, high pressuregas connector/valve 71, low-pressure gas connector/valve 73, and usercontrol panel 74. The basic operation (after probe 1 and introducersheath 2 is placed in operational position as previously described, andthe system has been purge of air as described in detail below) is asfollows:

-   -   1) Cerebrospinal fluid 19 (FIG. 1) is drawn into cooling        cylinder 72 of cooling assembly 3 through fluid port 26 and        probe shaft 21 by movement of piston 48 from position (1) (shown        in dashed lines) to position (2) (shown in solid lines).        (Cooling cylinder 72 of cooling assembly 3 is connected to        pneumatic cylinder 58 of control console 76 by pneumatic gas        line 37. Pneumatic piston 59 is actuated from position (1)        (shown in dashed lines) to position (2) (shown in solid lines)        by crank 56, connecting rod 57, and motor 55. Pneumatic coupling        between cooling cylinder 72 and pneumatic cylinder 58 causes        piston 48 to move from position (1) to position (2) when        pneumatic piston 59 is actuated from position (1) to position        (2).)    -   2.) High-pressure solenoid valve 64 is opened allowing high        pressure gas to enter cooling coil assembly 47. Cerebrospinal        fluid 19 contained in cooling cylinder 72 is then cooled by        cooling coil assembly 47 by thermal conduction of heat through        the walls of cooling cylinder 72 into cooling coil assembly 47.        (Detailed description of cooling mechanism is described in        description of FIG. 8 below).    -   3.) When the cerebrospinal fluid 19 in cooling cylinder 72 is        cooled to predetermined temperature (5 Deg. C. to 30 Deg. C.) as        sensed by thermocouple 45 of cooling assembly 3, high-pressure        solenoid valve 64 is closed thereby stopping the cooling        process, and pneumatic piston 59 is actuated from position (2)        to position (1) causing piston 48 to move from position (2) to        position (1) which reintroduces the cooled cerebrospinal fluid        into ventricle 6.    -   4.) After a predetermined time to allow for thermal diffusion (5        to 60 seconds) the temperature of the cerebrospinal fluid 19 in        ventricle 6 is measured by thermocouple 18. If after this period        of time the temperature of the cerebrospinal fluid 19 in        ventricle 6 is above a predetermined temperature (20 Deg. C. to        35 Deg. C.) the cycle (steps 1-3 above) is repeated. If the        temperature of the cerebrospinal fluid 19 in ventricle 6 remains        at or below the predetermined temperature after the time allowed        for thermal diffusion, ventricle temperature is continuously        monitored by thermocouple 18. The cycle (steps 1-3 above) is        repeated once the temperature of the cerebrospinal fluid 19 in        ventricle 6 rises above the predetermined value as described        above. Cooling coil assembly 47 removes heat from cooling        cylinder 72 by a cooling process commonly known as        Joule-Thompson effect where gas (nitrogen, argon, or a mixture        of nitrogen and argon) is expanded from a high-pressure to        low-pressure within the cooling coil assembly 47 (FIG. 8).        Cooling gas is supplied to cooling coil assembly 47 from the        control console 76 at a pressure between 200 pounds per square        inch absolute (PSIA) and 1600 PSIA by high-pressure tube 35        contained in umbilical 14 (FIGS. 1 & 2). Expanded low-pressure        gas (5 to 100 PSIA) is returned to the control console 76 by        low-pressure tube 36 contained in umbilical 14. Prior to use,        the probe 1 and cooling assembly 3 is connected to the control        consol 76 by umbilical 14 and umbilical connector 69 (shown in        schematic form). After connecting umbilical 14 to control        console 76 the system is purged of air, and cooling piston 48 is        moved into position 1 as follows:    -   1.) Pneumatic piston 59 is moved into position (1) by motor 55,        crank 56, and connecting rod 57. Position transducer 54 provides        control circuitry 53 with a signal indicative of pneumatic        piston 59 position.    -   2.) High-pressure solenoid valve 64 is then opened allowing        cooling gas to flow into cooling coil assembly 47 at high        pressure, and cooling gas to flow from cooling coil assembly 47        at low pressure back to the control console thereby displacing        air from cooling coil 47, and gas lines 35, 36, 65, and 66.    -   3.) After a predetermined period of time (20 to 60 seconds) to        allow for complete purging of air, low-pressure solenoid valve        63 is opened forcing cooling piston 48 into position (1).        Low-pressure solenoid valve 63 is then closed, leaving both        pneumatic piston 59, and cooling piston 48 in position (1).    -   4.) Probe 1 is then placed into brain ventricle 6 as previously        described and cerebrospinal fluid 19 is drawn from ventricle 6        by syringe (not shown) through fluid tube 15 and luer fitting 25        (FIG. 2A) to remove air from probe shaft 21.

Control console 76 is connected to a source of high-pressure cooling gasby high-pressure valve/connector 71. Low-pressure gas is vented to theroom trough low-pressure valve/connector 73. Electrical power issupplied to the control console by power source 60, which is normally anAC wall outlet. Transformer 61 transforms voltage from local standard ACvoltage (120 or 240 volts) to system operating voltage (5 to 21 V).Control circuit 53 contains rectifier circuitry to transform sourcevoltage from AC to DC. User control panel 74 contains user controls andoperational display of system function. The user control panel providesfor a means to set the desired temperature of the cerebrospinal fluid 19in ventricle 6, a means to display the temperature of cerebrospinalfluid 19 in ventricle 6, a means to set the duration for cooling thecerebrospinal fluid 19 in ventricle 6, a means to set the rate ofcooling and rewarming of cerebrospinal fluid 19 in ventricle 6, a meansto initiate the air purge cycle as described above, and a means to turnthe cooling cycle on and off. It obvious to those skilled in the art ofelectronic design how to design the electronic circuits, user controls,and how to specify the appropriate components to provide systemfunctionality as described above. Those familiar with the art ofmechanical design know how to design the pneumatic cylinder 58, todesign the pneumatic piston 59 actuation mechanisms, to specify theappropriate motor 55 and position transducer 54, to specify theappropriate valves 71, 73, 64, & 63, to specify the appropriate gaslines 65, 66, and 68, and how to physically integrate all systemcomponents into a console configuration to provide system functionalityas described above.

Description FIGS. 7-18 Preferred Construction Embodiments

FIG. 7 depicts in a partial sectional view the cooling cylindersub-assembly 62 of cooling assembly 3. Cooling cylinder sub-assembly 62consists of cooling cylinder 72, piston 48, cylinder cap 66, pneumaticstem 67, cooling coil assembly 47, thermocouple 45, thermocouple leads77, fluid manifold 78, O-ring 79, O-ring 80, and silver solder 81.Cylinder 72, and cylinder cap 66 are machined from a copper allow tomaximize thermal heat transfer to cooling coil assembly 47. Aftermachining, cylinder 72 and cylinder cap 66 are plated with gold toprovide for biocompatibility. Cylinder 72 has an inner diameter between0.4 inches and 1.0 inches. Cylinder 72 has a wall thickness between 0.02inches and 0.1 inches. The length of cylinder 72 is between 1.5 and 4inches. The displacement of piston 48 in cylinder 72 is between 1 cc and5 cc. Piston 48 is machined or molded from a medical grade polymer suchas nylon, but may also be machined from a metal alloy. The outerdiameter of piston 48 is between 0.001 and 0.015 inches smaller than theinner diameter of cylinder 72. O-Ring 80 pneumatically isolates one sideof piston 48 from the opposite side, and resides in an appropriatelysized gland formed in piston 48 as shown. The length of piston 48 isbetween 0.5 and 1.5 its outer diameter. The construction of cooling coilassembly 47 is described in detail in FIGS. (8 & 9). O-ring 79 residesin a gland formed in cylinder cap 66 during the machining process andprovides for a pneumatic seal between the cylinder 72 and the cylindercap 66. Fluid manifold 78 is formed from type 304 stainless steel tubingand provides for fluid connection between fluid tube 13 and fluid tube15 (FIG. 1) and cylinder 72. The inner diameter of fluid manifold 78 isbetween 0.06 and 0.08 inches in diameter, and the walls of fluidmanifold 78 are between 0.002 and 0.005 inches thick. Pneumatic stem ismade from type 304 stainless steel and has an inner diameter of 0.08 to0.12 inches in diameter and has a wall thickness of 0.002 to 0.005inches thick. The cooling cylinder sub-assembly is assembled as follows:1.) Fluid manifold 78 is inserted into end hole 85 in cylinder 72 andsoldered into place with silver solder 81. 2.) Cooling coil assembly 47is soldered to cylinder 72 with silver solder 81 as shown. 3.)Thermocouple 45 is inserted into cylinder end hole 83 and glued in placewith silicon rubber adhesive 86. 4.) O-ring 80 is mounted to piston 48.Piston 48 is then inserted into cylinder 72. 5.) O-ring 79 is mounted oncylinder cap 66. Cylinder cap is then inserted into cylinder as shownand crimped into place with dimple crimps 82 as shown.

FIG. 8 depicts a sectional view of the construction of cooling coilassembly 47 prior to the coiling operation. Cooling coil assembly 47consists of manifold 50, low-pressure tube 88, high-pressure tube 89,end cap 90, silver solder 91, high-pressure stub 52, and low-pressurestub 51. Manifold 50, and end cap 90 are machined from type 304stainless steel as shown. Low-pressure tube 88, high-pressure tube 89,high-pressure stub 52, and low-pressure stub 51 are made from type 304stainless steel tubing. Low-pressure tube 88 has an inner diameter of0.09 to 0.12 inches, and has a wall thickness between 0.02 and 0.05inches. High pressure tube 89 has a inner diameter of 0.03 and 0.06inches and has a wall thickness of 0.002 and 0.005. High-pressure stub52 and low-pressure stub 51 have an inner diameter of 0.06 and 0.10inches, and has a wall thickness of 0.002 to 0.005. High-pressure tube89 has a least one hole drilled through the wall to form gas expansionorifice 96. Gas expansion orifice 96 is between 0.002 and 0.008 inchesin diameter. Cooling coil assembly 47 is assembled as follows: 1.)High-pressure tube 89, and low pressure tube 88 are soldered to end cap90 as shown with silver solder 91. 2.) High-pressure stub 52 and lowpressure stub 51 are soldered to manifold 50 as shown with silver solder91. 3.) Manifold 87 is then soldered to high-pressure tube 89 andlow-pressure tube 88 as shown with silver solder 91. The length (frommanifold 50 to end cap 90) of the cooling coil assembly 47 prior tocoiling is between 3 and 8 inches. Gas at high pressure entershigh-pressure tube 89 and forms high-pressure zone 95 through manifold50 and high-pressure stub 52 and is expanded to a low pressure inlow-pressure zone 94. Gas from low-pressure zone 94 is exhausted throughmanifold 50 and low-pressure stub 51, and ultimately to the room aspreviously described. During gas expansion from high pressure to lowpressure heat is lost according to the Joule-Thompson principle causingthe temperature of the expanded gas to be lowered, thereby cooling thewalls of low-pressure tube 88 causing absorbs ion of heat from coolingcylinder 72 as previously described.

FIG. 9 depicts the cooling coil assembly 47 after coiling operation. Thecoiling accomplished by wrapping the assembly around a mandrel. Theinner diameter of the coil in relaxed state is 0.010 to 0.030 inchessmaller than the outside diameter of cooling cylinder 72 to ensureintimate contact between cooling coil assembly 47 and cooling cylinder72.

FIG. 10A depicts a sectional view of the construction of the coolingassembly 3. FIG. 10B shows an end view of cooling assembly 3 prior toattachment of umbilical assembly 14. Cooling assembly 3 consists ofcooling cylinder sub-assembly 62, probe 1 (see FIGS. 12A & 12B forconstruction details) cooling assembly housing 97, cooling assemblymounting plate 27 (See FIG. 18 for construction detail), mounting pads28, fluid tube crimp ring 98, stop cock assembly 99 which consists offluid tube 15, stop cock 19, and luer fitting 25, and crimp ring 100.Cooling assembly 3 is formed as follows: 1.) Fluid tube 13 of probe 1 ismounted to fluid manifold 78 of cooling cylinder sub-assembly 62 asshown, and is held in place with crimp ring 100. 2.) Cooling cylindersub-assembly, probe 1, mounting plate 27 are mounted into injection moldand cooling assembly housing 97 is formed by standard injection moldingprocess. Housing 97 may be made any suitable thermoplastic such as nylonor high density polyethylene. Stop cock assembly 99 which consists offluid tube 15, stop cock 19, and luer fitting 25 is attached to manifold78 and held in place with crimp ring 98. Stopcock assembly 99 is readilyavailable from many OEM medical device suppliers. Mounting pads 28 arecommon rubber grommets and are inserted into mounting holes 102 inmounting plate 27. Holes 101 are then drilled and tapped.

FIG. 11A depicts the attachment of the umbilical assembly 14 to thecooling assembly 3. FIG. 11B depicts the umbilical plug assembly 120.FIG. 11C, 11D, and 11E depicts radial sections of umbilical plugassembly 120. FIG. 11F depicts a transverse section of umbilical plugassembly 120. FIG. 11G depicts the removable connection mechanism ofumbilical assembly 14 to control console 76. Umbilical assembly 14consists of umbilical flange 161, umbilical sheath 92, umbilical plugassembly 120, thermocouple connectors 107 and 108, high-pressure tube35, low-pressure tube 36, pneumatic tube 37, thermocouple lead 34,thermocouple lead 77, thermocouple lead sheath 126 and 127, sheathretainer 121, tube crimp rings 105, silicone rubber compound 104, screw103, and epoxy adhesive 106. The umbilical assembly 14 is between 3 and8 feet long. The umbilical sheath 92 is vinyl tubing with an innerdiameter of 0.25 to 0.375 inches and has a wall thickness of 0.010 to0.025 inches. Umbilical flange 161 is injection molded from a suitablethermoplastic such as nylon. One end of umbilical sheath 92 is attachedto umbilical flange 161 with epoxy adhesive 106 as shown. High pressuretube 35 is 0.125 to 0.31 inches in outer diameter and has a wallthickness of 0.025 to 0.040 inches in diameter and is made from nylon.Low-pressure tube 36, and pneumatic tube 37 are 0.125 to 0.31 inches inouter diameter with a wall thickness of 0.010 to 0.015 inches and aremade of nylon. Parker Hannifin Corp. manufactures a full line suitabletubing under the brand name Parflex that is suitable for use for tubes35, 36 and 37. Thermocouple leads 34 and 77 are selected forcompatibility with thermocouples 45 and 18. Omega Corp. manufacturesthermocouples, and thermocouple leads suitable for the application.Tubes 35, 36, and 37, and thermocouple leads 34 and 77 inserted intoumbilical sheath 92 such that tubes 35, 36 and 37, and thermocoupleleads 34 and 77 protrude past both ends of umbilical sheath 92 andumbilical flange 161 2 to 3 inches. High-pressure tube 35 is attached tohigh-pressure stub 52 of cooling assembly 3 and crimped into place withstainless steel crimp ring 105. Low-pressure tube 35 is attached tolow-pressure stub 51 of cooling assembly 3 and crimped into place withstainless steel crimp ring 105. Pneumatic tube 37 is attached topneumatic stub 67 of cooling assembly and crimped into place withstainless steel crimp ring 105. Thermocouple leads 34 and 77 are spotwelded to thermocouple leads from thermocouple 18 and 45 respectively,and silicone rubber 104 is used to electrically insulate the weldjoints. Umbilical flange 161 is then bolted to cooling assembly 3 withscrews 103. Plug assembly 120 is attached to the opposite end theumbilical assembly 14 and provides removable connection of the coolingassembly 3 to the control console 76. FIG. 11B-11F depicts the plugassembly 120. Plug assembly 120 consists of: plug tube 129, end cap 125,plug handle 119, sheath retainer 121, crimp ring 128, bulkhead 130,bulkhead 131, bulkhead 132, pneumatic tube 134, low-pressure tube 133,high-pressure tube 135, crimp ring 105, thermocouple lead sheath 126 &127, thermocouple connectors 107 and 108, vinyl adhesive 137, epoxyadhesive 138, silver solder 136. Bulkhead 130 and end cap 125 formpneumatic gas chamber 139, bulkhead 130 and bulkhead 131 form highpressure gas chamber 140, bulkhead 131 and bulkhead 132 formlow-pressure gas chamber 141. Pneumatic tube 134 connects pneumatic tube37 to pneumatic gas chamber 139. High-pressure tube 135 connectshigh-pressure tube 35 to high-pressure gas chamber 140. Low-pressuretube 133 connects low-pressure tube 36 to low-pressure chamber 141.Pneumatic port 124, high-pressure port 123, and low-pressure port 122provide gas communication with console receptacle 110 (FIG. 11G).Bulkheads 130, 131, 132, end cap 125, and plug handle are machined fromtype 304 stainless steel. Pneumatic tube 134, low-pressure tube 133, andhigh-pressure tube 135 are stainless steel with 0.125 to 0.187 inchouter diameter with 0.010 to 0.020 wall thickness. Plug tube 129 issoldered to plug handle 119 with silver solder 136. End cap 125 issoldered to plug tube 129 with silver solder 136. Bulkhead 130, issoldered to pneumatic tube 134 with silver solder 136. Bulkhead 131 issilver soldered to pneumatic tube 134 and high-pressure tube 135.Bulkhead 132 is soldered to pneumatic tube 134, high-pressure tube 135,and low-pressure tube 133. The soldered assembly described above isinserted into plug tube 129 as shown and is swaged by a rotary swager toform a seal between bulkheads 130, 131, and 132 and plug tube 129.Thermocouple leads 34 and 77 exit umbilical sheath 92 approximately 6inches from umbilical plug assembly 120 and are reinforced with vinylsheaths 126 and 127 whch are retained by vinyl adhesive 137 as shown.Pneumatic tube 37 is attached to pneumatic tube 134 with crimp ring 105.High-pressure tube 35 is attached to high-pressure tube 135 with crimpring 105. Low-pressure tube 36 is attached to low-pressure tube 133 withcrimp ring 105. Vinyl sheath retainer 121 is glued to umbilical sheath92 with epoxy 138, and fixated to plug handle 119 with stainless steelcrimp ring 128. FIG. 11G depicts the construction of the control console76 plug receptacle assembly 110 in functional relationship withumbilical plug assembly 120. Plug receptacle assembly 110 consists ofmanifold 142, pneumatic stem 115, high-pressure stem 117, low-pressurestem 118 and O rings 114, 113, 112, and 111. Stems 115, 117 and 118 arestainless steel tubes 0.125 to 0.187 inch outer diameter with 0.010 to0.015 wall thickness. Stems 115, 117, and 118 are silver soldered tomanifold 142 with silver solder 116 as shown. O-rings 114 and 113provide gas communication to console 76 pneumatic line 68 as shown.O-rings 113 and 112 provide gas communication to console 76high-pressure line 65 as shown. O-rings 112 and 111 provide gascommunication to console 76 low-pressure line 66 as shown. Plugreceptacle assembly 110 is mounted to control console 76 control panel74 with hardware as shown. Thermocouple leads 34 and 77 are connected tothe control console by standard thermocouple plugs 107 and 108 viestandard thermocouple receptacles (not shown).

FIG. 12A depicts a sectional view of probe 1. FIG. 12B depicts asectional view of probe shaft 21. Probe 1 consists of shaft 21, probetube 13, sheath docking collar 24, sheath expansion plug 29,thermocouple 18, and thermocouple lead 34. Probe shaft 21 is extrudedfrom high density polyethylene and has two lumens. Lumen 32 is thecerebrospinal fluid 19 channel. Lumen 33 contains thermocouple leads 34and thermocouple 18 at distal end 7. Probe shaft 21 is 1.0 to 1.5 mm indiameter. Lumen 32 is 0.7 to 1.0 mm in diameter. Lumen 33 is 0.2 to 0.3mm in diameter. The length of probe shaft is 3 to 10 cm. Distal end 7 isclosed by melting process commonly referred to as tip forming by thoseskilled in the art catheter making. A stainless steel mandrel occupieslumen 32 during the tip forming process which maintains the shape oflumen 32 as shown. Thermocouple 18 is secured during tip forming bymelting and collapsing lumen 33. A milling process forms fluid port 26.Sheath docking collar 24 is injection molded of a nylon compound. Sheathexpansion plug 29 is stainless steel tubing who's inside diameter isequal to the outside diameter of probe shaft 21 and has a wall thicknessof 0.015 to 0.030 inches. Sheath expansion plug 29 is integrated withsheath docking collar 24 by insert molding technique during moldingprocess. Fluid tube 13 is a continuation of probe shaft 21. Probe shaft21 and fluid tube 13 are fastened to sheath docking collar 24 and sheathexpansion plug 29 with adhesive 143.

FIG. 13 shows a bottom view of probe 1 depicting the sheath/housingdocking mechanism. Introducer sheath docking pins 42 (FIG. 3) enterpinhole 93 in docking collar 24. The probe 1 is then rotated 45 degreesin the direction shown to lock probe 1 to introducer sheath 2.

FIG. 14 depicts a sectional view of the introducer sheath 2. Theintroducer sheath consists of the sheath/probe docking ring assembly 147(See FIG. 15 for construction details), introducer sheath tube assembly144 (See FIG. 16 for construction details) Antiseptic pad 145, andintroducer sheath housing 40. The introducer sheath assembly, except theantiseptic pad is formed by placing the sheath/probe docking ringassembly 147, and introducer sheath tube assembly 144 into a fixturingmold and casting the introducer sheath housing 40 to form the integratedassembly. The introducer sheath housing 40 is cast from a two-partmedical grade silicon rubber with a hardness of between 40 and 60durometer. Dow-Corning Corporation manufactures a full line of medicalgrade silicon rubber suitable for this application. The antiseptic pad145 is made from open cell foam, and is saturated with antiseptic fluideither at the factory, or in the field prior to use. Antiseptic foam pad145 is between 10 and 20 durometer in hardness. A suitable antisepticfluid is an iodine solution marketed under the registered trade nameBetadine. The foam pad 145 may be glued to the bottom face of theintroducer housing 40 with a suitable adhesive.

FIG. 15A shows a sectional view of the sheath/probe docking ringassembly 147. The sheath/probe docking ring assembly 147 consists oftype 304 stainless steel docking ring 148 and two type 304 stainlesssteel docking pins 42. The docking ring 148 has a hole in the centerwhich mates with the sheath tube assembly 144 as shown in FIG. 14. Thedocking ring has (6) holes 149 which provides anchorage within theintroducer sheath housing 40 when the introducer sheath housing 40 ismolded around the sheath/probe docking assembly 147. The docking pins 42are welded to the docking ring 148.

FIG. 16 shows a sectional view of the introducer sheath tube assembly144. The introducer sheath tube assembly 144 consists of the sheath tube8, and the sheath ferrule 150. The sheath tube 8 and the sheath ferrule150 are made of high density polyethylene or other suitablethermoplastic. The sheath tube is extruded into tubular form by standardmeans, and then blow molded into final shape. The wall thickness of thesheath tube 8 is between 0.001 and 0.002 inches. The inside diameter ofthe sheath tube 8 at the distal end is 0.020 to 0.025 inches greaterthan the diameter of the probe shaft 21 it is designed to mate with. Theinside diameter of the sheath tube at the proximal end is 0.001 to 0.004inches smaller than the sheath expansion plug 29 of probe 1 that it isdesigned to mate with. The sheath ferrule 150 is injection molded and isbonded to sheath tube 8 by standard ultrasonic welding techniques.

FIGS. 17 a and 17B depicts the system control console 76. The controlconsole 76, contains a source for cooling gas (argon or nitrogen) inmultiple, replaceable tanks 151. The gas tanks 151 are connected to theconsole 76 using common medical grade pressure regulators 152. Thecontrol console 76 has a control panel 74, which provides forcerebrospinal fluid 19 temperature display means 158, and a means todisplay relative cooling power (0% to 100% of maximum heat removalcapacity) 159. The control panel has a means to adjust the cerebrospinalfluid 19 temperature setting 160. The control console may be constructedto provide for operation of multiple probes 1 simultaneously by means ofmultiple display and control channels 157. The control console 76 hasmeans to removably connect the probe umbilical 14 to the controlconsole, where the connection means is by gas plug 120 on the end of theprobe umbilical cable 14, and gas plug receptacle 110 mounted on thefront of the control panel 74. The control console also provides anelectrical connection means for the probe tip thermocouple leads 34 and77 by the thermocouple receptacle 154 and 155 on the control panel 74.

FIG. 18 depicts the construction of mounting plate 27. Mounting plate 27is made from stainless steel sheet and is 0.005 to 0.010 inches thick.

ALTERNATE EMBODIMENTS

A fluid pump may be used, instead of a syringe mechanism as described inthe preferred embodiment, in conjunction with a probe that contains 2fluid channels, or multiple probes, to continuously remove, replace andcool cerebrospinal fluid. The cerebrospinal fluid cooling mechanism mayplaced in the control console, or further away from the head than asdescribed in the preferred embodiment. The method of cooling may beother than Joule-Thompson effect.

ADVANTAGES

From the description above there are a number of advantages my methodand apparatus for treating secondary brain injury provide:

-   -   (a) The therapeutic agent (hypothermia) for preventing secondary        injury according to this invention is applied directly to the        brain.    -   (b) The therapeutic agent (hypothermia) for preventing secondary        injury according to this invention is limited to the brain.    -   (c) Lower hypothermic temperatures can be practically achieved        in the brain than can be achieved by the methods currently        described in the art since only the brain is exposed to        hypothermia.    -   (d) Lower hypothermic temperatures can be achieved in the brain        than with methods described in the art.    -   (e) Hypothermic temperatures can be maintained longer in the        brain than with methods described in the art.    -   (f) Hypothermic temperatures can be achieved in the brain by        means of a single small caliber-cooling probe.    -   (g) The degree of hypothermia in the brain can be adjusted        according to the physiological response to hypothermia.    -   (h) Ventricle cooling may be accomplished without introducing        extra-corporeal fluids.

1-20. (canceled)
 21. A brain probe assembly, comprising: a probedefining a lumen and having a distal end configured to insert within abrain ventricle; and a cooling assembly coupled to the probe, thecooling assembly operable to remove fluid from the brain ventricle viathe probe, adjust a temperature of the fluid, and return the fluid tothe brain ventricle via the probe.
 22. The brain probe assembly of claim21, wherein the brain probe assembly further comprises a fixation deviceoperable to couple the probe to a cranium.
 23. The brain probe assemblyof claim 22, wherein the fixation device comprises a fixation plugconfigured to insert within a craniotomy formed in the cranium.
 24. Thebrain probe assembly of claim 21, wherein the probe comprises atemperature sensor.
 25. The brain probe assembly of claim 21, whereinthe probe comprises a pressure sensor.
 26. The brain probe assembly ofclaim 21, wherein the probe comprises a drainage assembly in fluidcommunication with the lumen defined by the probe.
 27. The brain probeassembly of claim 21, wherein the probe comprises an antiseptic paddisposed on a proximal end of the probe.
 28. The brain probe assembly ofclaim 21, wherein the brain probe assembly further comprises a fixationdevice operable to couple the cooling assembly to a cranium.
 29. A brainprobe system, comprising: a probe defining a lumen and having a distalend configured to insert within a brain ventricle; a cooling assemblycoupled to the probe, the cooling assembly operable to remove fluid fromthe brain ventricle via the probe, adjust a temperature of the fluid,and return the fluid to the brain ventricle via the probe; and acontroller configured to detect a state of the fluid of the brainventricle and operate the cooling assembly based upon the detectedstate.
 30. The brain probe system of claim 29 wherein the controller isconfigured to detect a temperature of the fluid and operate the coolingassembly until the detected temperature approaches a thresholdtemperature.
 31. The brain probe system of claim 29 wherein thecontroller is configured to detect a pressure of the fluid and operatethe cooling assembly until the detected pressure approaches a thresholdpressure.
 32. The brain probe system of claim 29, wherein the systemfurther comprises a fixation device operable to couple the probe to acranium.
 33. The brain probe system of claim 32, wherein the fixationdevice comprises a fixation plug configured to insert within acraniotomy formed in the cranium.
 34. The brain probe system of claim29, wherein the probe comprises a temperature sensor.
 35. The brainprobe system of claim 29, wherein the probe comprises a pressure sensor.36. The brain probe system of claim 29, wherein the probe comprises adrainage assembly in fluid communication with the lumen defined by theprobe.
 37. The brain probe system of claim 29, wherein the probecomprises an antiseptic pad disposed on a proximal end of the probe. 38.The brain probe system of claim 29, wherein the system further comprisesa fixation device operable to couple the cooling assembly to a cranium.39. A method for inducing cerebral hypothermia, comprising: inserting aprobe within a brain ventricle, the probe defining a lumen; removingfluid from the brain ventricle via the probe; adjusting a temperature ofthe fluid removed from the brain; and returning the fluid to the brainventricle via the probe.
 40. The method of claim 39 wherein adjustingcomprises adjusting a temperature of the fluid removed from the brainventricle based upon a state of the fluid.
 41. The method of claim 40wherein adjusting comprises adjusting a temperature of the fluid removedfrom the brain ventricle based upon a temperature of the fluid.
 42. Themethod of claim 40 wherein adjusting comprises adjusting a temperatureof the fluid removed from the brain ventricle based upon a pressure ofthe fluid.